When color photographic light-sensitive materials are intended to be more or less permanently balance of yellow, magenta, and cyan dye images be equal to the initial three color balance by minimizing light discoloration and dark discoloration. However, since the Yellow, magenta, and cyan dye images show different degrees of light and dark discoloration, the balance of these three colors is often lost through long-term preservation, thus deteriorating image qualities.
Degrees of light and dark discoloration naturally differ depending on the couplers used in the light-sensitive materials and other factors. In many cases, however, dye images tend to undergo dark discoloration in the order of cyan dyes, yellow dyes, and magenta dyes. The degree of dark discoloration of a cyan dye image is particularly greater than those of other dye images. Likewise, dye images tend to undergo light discoloration in the order of cyan dye images, yellow dye images, and magenta dye images, particularly when exposed to light rich in ultraviolet rays.
With these considerations in mind, it has been keenly demanded to minimize such light and dark discoloration of cyan dye images in order to better balance the degrees of discoloration of yellow, magenta, and cyan colors. Many attempts have been made to this effect. These conventional attempts can be classified into two categories, one being directed to developing couplers that may form dye images free from discoloration; the other being to develop additives that may prevent discoloration.
In particular, an improvement as to preventing dark discoloration of cyan dye images is of great commercial importance, as is apparent from the need to preserve photographs (e.g., in albums, etc.) in home life for extremely long periods of time. Various proposals have been made thus far to attain such a result; however, effects to although some progress has been made, the effects of such efforts are not satisfactory.
A number of cyan dye forming phenol couplers are known. For example, 2-["-2,4-di-t-amylphenoxybutaneamido]-4,6-dichloro-5-methyl-phenol, disclosed in U.S. Pat. No. 2,801,171, produces cyan dye images which are satisfactory in light-fastness, but inferior in heat-fastness.
Further, 2,5-diacylaminophenol cyan couplers having acylamino groups at the 2- and 5-positions of the phenol nucleus are disclosed, e.g., in U.S. Pat. Nos. 2,369,929, 2,772,162 and 2,895,826, and Japanese Patent Application (OPI) Nos. 112038/75 (U.S. Pat. No. 4,009,035), 109630/78 (U.S. Pat. No. 4,124,396) and 163537/80 (U.S. Pat. No. 4,299,914) (the term "OPI" as used herein means a "published unexamined Japanese patent application"). Although these 2,5-diacylaminophenol couplers produce cyan dye images having satisfactory light-fastness, they also result in the disadvantages of poor color developability, light discoloration of resulting cyan dye images, and undesirable yellowing arising from the light-irradiation of unreacted cyan couplers. Further, these 2,4-diacylaminophenol couplers could be improved as to heat-fastness.
1-Hydroxy-2-naphthamide cyan couplers are generally unsatisfactory in terms of both light discoloration and dark discoloration of resulting images.
1-Hydroxy-2-acylaminocarbostyril cyan couplers, as disclosed in Japanese Patent Application (OPI) No. 104333/81, form cyan dye images which exhibit satisfactory fastness to light and heat, but whose spectral absorption characteristics do not favor color reproduction. Moreover, such couplers have problems, such as pink stain formation upon light irradiation.
The cyan polymeric couplers described in U.S. Pat. No. 3,767,412 and Japanese Patent Application (OPI) Nos. 65844/84 and 39044/86 are superior in heat-fastness under dry conditions, but inferior in heat-fastness under high humidity conditions, and are also insufficient in color developability.
Phenol couplers substituted with an alkyl group having 2 or more carbon atoms at the m-position thereof, as described in Japanese Patent Publication No. 11572/74, Japanese Patent Application (OPI) Nos. 117249/85, 205446/85, 209735/85 and 39045/86, are excellent in heat-fastness, but still insufficient.
On the other hand, when these couplers are incorporated into silver halide emulsion layers, they are commonly dispersed in high-boiling point organic solvents, as described in U.S. Pat. Nos. 2,322,027, 2,801,117, 2,870,012 and 2,991,177, etc. It is believed, however, that transfer of the high-boiling point organic solvents or couplers to other layers is one of the causes of deterioration in photographic properties and film properties of photographic materials, particularly multilayer light-sensitive materials, when preserved under conditions of high temperature and high humidity. Therefore, the use of high-boiling point organic solvents for dispersion is likely to result in such deterioration.
Polymers may be used for dispersing couplers in place of such high-boiling point organic solvents, as described in Japanese Patent Publication No. 30494/73 (U.S. Pat. No. 3,619,195) and Japanese Patent Application (OPI) No. 25133/76 (U.S. Pat. No. 4,201,589). Although the use of these techniques has brought about some improvement as to image preservability, the effects attained are still insufficient. For example, the present inventors have determined that the copolymers comprising hydrophilic monomers, e.g., acrylic acid, as disclosed in Japanese Patent Publication No. 30494/73, deteriorate image preservability under conditions of high temperature and high humidity
It is further taught, e.g., in U.S. Pat. No. 4,203,716, that a hydrophobic substance, such as an oil-soluble coupler, is dissolved in a water-miscible organic solvent, and the solution is then mixed with a polymer latex to thereby impregnate the polymer with the hydrophobic substance. However, this technique encounters the problem that resultant cyan dye images are inferior in light-fastness, as compared with the case of using water-immiscible high-boiling point organic solvents. In addition, a large quantity of the polymer would be required to obtain sufficient impregnation of couplers thereinto to obtain sufficiently high maximum color density.